Fluorinated hydrocarbons have many uses, one of which is as a refrigerant. Such refrigerants include dichlorodifluoromethane (CFC-12) and chlorodifluoromethane (HCFC-22).
In recent years it has been suggested that certain chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) refrigerants released into the atmosphere may adversely affect the ozone layer. Although this proposition has not yet been completely established, there is a movement toward the control of the use and the production of certain CFCs and HCFCs under an international agreement.
In order to address the potential problem of ozone depletion, it has been suggested that chlorofluorocarbon refrigerants and hydrochlorofluorocarbon refrigerants be replaced with hydrofluorocarbon refrigerants. Since the hydrofluorocarbon (HFC) refrigerants contain no chlorine, they have zero ozone depletion potential.
Another environmental concern is the role of CFCs in the "greenhouse effect". The greenhouse effect refers to the warming of the Earth's climate that takes place when atmospheric gases, which are relatively transparent to visible light and allow sunshine to reach the Earth, trap heat by absorbing infrared radiation released by the Earth.
There is presently no universally accepted methodology for combining all relevant factors into a single global warming potential for emissions of gases such as CFCs. One approach is to define the greenhouse effect of a compound in terms of a potential to enhance global warming relative to a known standard. One such definition is known as a halocarbon global warming potential (HGWP), which is the ratio of incremental radiative warming resulting from an emission of a gas, over the lifetime of the gas in the atmosphere, to the calculated warming that would result from a release of the same mass of reference gas CFC-11.
While HFCs may have a zero ozone depletion potential, some HFCs may have an HGWP that may be undesirable and subject to governmental regulation. Accordingly, there is also a demand for the development of refrigerants that have a low ozone depletion potential while at the same time having a low HGWP.
It is preferred that refrigerants that include more than one component be azeotropic or azeotrope-like so that the composition of the refrigerant does not change when leaked or discharged to the atmosphere from refrigeration equipment. A change in composition of a refrigerant may affect its properties, such as performance or flammability.
It is also desirable to use compositions that have a low ozone depletion potential and/or a low HGWP and/or that are azeotropic or azeotrope-like as cleaning agents, blowing agents in the manufacture of closed-cell polyurethane, phenolic and thermoplastic foams, as propellants in aerosols, as heat transfer media, gaseous dielectrics, fire extinguishing agents, power cycle working fluids, such as for heat pumps, inert media for polymerization reactions, fluids for removing particulates from metal surfaces, as carrier fluids that may be used, for example, to place a fine film of lubricant on metal parts, or as buffing abrasive agents to remove buffing abrasive compounds from surfaces such as metal, as displacement drying agents for removing water, such as from jewelry or metal parts, as resist developers in conventional circuit manufacturing techniques including chlorine-type developing agents, and as strippers for photoresists when used with, for example, a chlorohydrocarbon, such as 1,1,1-trichloroethane or trichloroethylene.